Advanced Materials Research Vols. 255-260

Abstract: Numerical investigations of multiphase irregular wave field are presented by using the BEM, which incorporates the interaction between incoming wave and reflected wave in the coastal area. This study discusses the case of multi-component wave generation using the 2D-NWT, which incorporates the wave-wave interactions between various conditions of incoming waves and high frequency reflected waves, including the variation of wave field and particle trajectory. The surf beats in the surf zone is mainly the cause of the cross-shore motion, and the generations of high frequency harmonics waves, these phenomena will be study accordingly in this preliminary study for the modeling of oscillations cause by surf beat and back swash, the generation of high frequency multi-phase reflected wave are carried out to investigate the deformation of wave profile, wave field and particle path-line.

Abstract: Based on researches on conventional analytical method of the Rayleigh wave testing data, the wavelet theory is introduced to analyze the data and we find that wavelet components of the Rayleigh wave testing data on the scale of 2^-1 and 2^-2 are high frequency interference, so we omit them. Afterwards, the coherent analysis, phase-different analysis and power spectrum analysis of the smoothing signal on the scale of 2^-2 are made to obtain the frequency dispersion curve, which is smoother and more reasonable than that obtained without using wavelet denoising. Besides, the testing data of shear wave is closer to the calculated value. The results indicate that applying wavelet analysis to the disposal of the Rayleigh wave testing data works efficiently.

Abstract: A new 3-dimensional isolation bearing (3DIB), which is combined with lead rubber bearing (LRB) and disk spring bearing (DSB), is introduced in this paper. A series of shaking table tests of the 1/2 scale fixed-base and 3DIB base-isolated model were compared to confirm the validity of the 3DIB. Results show that the 3DIB can isolate 3-dimensional earthquake energy remarkably. Large displacement of the 3DIB base-isolated system occurred on the isolation layer, and the inter-story deformation of the superstructure changed slightly. The horizontal acceleration responses of 3DIB model decreased more than 60% and the vertical acceleration responses decreased more than 50% under the severe earthquake of 0.4g in PGA input, which confirmed that 3DIB could isolate both the horizontal and vertical earthquakes obviously.

Abstract: The earthquake may attack the structural building from any angle, but in current seismic design codes, this type of uncertainty is seldom accounted. The uncertainty associated with the direction of earthquake excitation was considered in this paper, and its effect on structural responses was investigated. For this purpose, a simple 3-dimensional model with symmetric plan was established, which had fundamental periods ranged from 0.1s to 5.0s, and was subjected to a set of 30 ground motion pairs for which both linear and nonlinear time history analyses were performed. Analyzing results showed that, on average, the elastic roof acceleration is 32% underestimated, and the inelastic roof displacement is 18% underestimated if the variation of earthquake excitation direction is not consider. Recognizing this, a modification factor for the seismic demand was proposed thorough a statistical analysis, which guarantees a probability of 95% design safety

Abstract: The seismic responses of 6-storey frame structures which are designed by means of beam yield mechanism (BYM) and column yield mechanism (CYM) are compared by using pushover analysis and dynamic analysis. This paper discusses the influence of column- to- beam strength ratio on seismic performance of concrete filled tube moment-resistant frames and analyzes the probability of the column yield mechanism. The results indicate that the strength ratios between columns and beams in a layer are effective parameters and of great significance to form yield mechanism.

Abstract: This paper presents the performance of base-isolated steel structures under the seismic load. The main goals of this study are to evaluate the effectiveness of base isolation systems for steel structures against earthquake loads; to verify the modal analysis of steel frame compared with the hand calculation results; and development of a simulating method for base-isolated structure’s responses. Two models were considered in this study, one a steel structure with base-isolated and the other without base-isolated system. The nonlinear time-history analysis of both structures under El Centro 1940 seismic ground motion was used based on finite element method through SAP2000. The mentioned frames were analyzed by Eigenvalue method for linear analysis and Ritz-vector method for nonlinear analysis. Simulation results were presented as time-acceleration graphs for each story, period and frequency of both structures for the first three modes.

Abstract: In this paper, the application of artificial neural network (ANN) in predicting seismic response of reinforced concrete (RC) frames with masonry infilled walls is investigated. The objective of this research is to predict roof displacement and base shear (ANN outputs) in the target displacement. The total of 855 database were prepared for modeling neural network using finite element method (FEM) by changing six parameters (the input parameters of ANN) including the number of bays, the number of stories, thickness of masonry infill, infilled wall ratio, existence of soft story and design spectral acceleration. A training set of 513 prepared database were used as training data and the validation set of 342 database were used as validation data in the next step. In the present study, two ANNs were trained; a multilayer perseptron (MLP) with Levenberg–Marquardt (LM) back propagation algorithms and a Radial Basis function (RBF), both with different structures and the best structure for each of them was obtained. The performance of ANNs was evaluated using mean square error (MSE) and correlation coefficient (R²) criteria. Results indicate that using both MLP and RBF ANNs for predicting target displacement have been appropriate and have low error as well as high speed. Furthermore, RBF network has a higher speed in training process of data compared to MLP network.

Abstract: For vulnerability assessment of structures, different damage indexes have been established by researchers that estimate the structural damage level. In these indexes different parameters have been used for calculating structural damage level. In this paper, damage indexes based on deformation, energy and cycle hysteretic behavior are investigated in order to find a correlation between their numerical values. The selected damage indexes are calculated and compared by applying them in nonlinear time history analysis of low and intermediate rise knee braced steel frames subjected to a set of seven earthquake accelerograms. Correlations between various indexes have been presented graphically and approximate conversion formulas are also provided.

Abstract: Based on the current methods of damage detection, a new detection damage model was proposed in order to search a more efficient detection method for reinforced concrete high-rise building damage induced by earthquake. This model is based on the regularity of change in the damping ratio of high-rise buildings, and the high order modes, mode participation coefficient and measure method of natural frequency, together with the type of structures, are taken into account in the model. The shaking test results for a model of reinforced concrete high-rise buildings show that the damage detection results based on the proposed model are close to the test results.

Abstract: In 1960s, considerable teaching buildings were built by old seismic design on Chinese campus. After work more than 40 years, their current seismic capability needs further analysis. This paper assesses the capability of load and elastic deformation[1] of a teaching building, masonry structure, to discuss whether they can meet the higher seismic design requirements of the current codes. The study concentrates on three tasks: analytical investigation; test of compressive strength of bricks; comparatively studies using two PMCAD models with emphasis on ratio of resistance to effect, and data of inter-story displacement angle. The models were studied, namely, initial work phase model basing on seismic precautionary intensity VII and current work phase model basing on seismic precautionary intensity VIII. Results of this study provide preliminary information and recommendations for seismic assessment and strengthening of teaching buildings.